JP2004246099A - Method and device for displaying image, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption of an image display device by decreasing a light quantity of backlight without losing brightness of an image of the image display device in appearance. <P>SOLUTION: An image signal in an RGB format which is inputted from a control part 1, and an image signal which is emphasized on a brightness signal component through a conversion from the image signal in RGB format into that in YCbCr format in a converter part 2, an emphasis on the brightness component Y in a brightness emphasis part, and an inverse conversion into the RGB format in the inverse conversion part 4 are inputted to a multiplexer 5. When the control part 1 is set to an electric power saving mode for reducing the light quantity of backlight lower than normal, it controls a backlight power source 10 to reduce the light quantity of the backlight module; selects at the same time an image signal emphasized on the brightness signal component in a multiplexer 5 to write the signal to frame memory 6; and displays it on an LCD module 7 through reading. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display method, an image display device, and an electronic device, and more particularly to an image display method, an image display device, and an electronic device that can reduce power consumption when a backlight-illuminated image display device is used.
[0002]
[Prior art]
In an image display device that is often used in portable electronic devices such as a liquid crystal display device, it is extremely important to reduce power consumption. In particular, if the power consumption can be reduced by reducing the amount of light of the backlight, the effect is large. . However, the conventional control of the light amount of the backlight is performed solely from the viewpoint of improving the visibility of the screen, and adjusts the light amount to the brightness of the external light (for example, Patent Document 1 or Patent Document 2). reference.).
[0003]
Apart from this, it is also possible to extract the luminance signal component in the image signal by the image signal processing technique and to correct the luminance of the screen (for example, see Patent Document 3). The invention disclosed in Patent Document 3 does not multidimensionally correct the luminance of each color component in an RGB format in which an image signal is expressed by a color component, but temporarily converts the YUV into a luminance signal component and a color difference signal component. By converting the format and then correcting the brightness in a unified manner, it is possible to perform fine-grained brightness correction with a simpler circuit, with the aim of eliminating uneven brightness in large-screen television receivers. I have.
[0004]
In addition, there is one that performs image signal processing and backlight light amount control (for example, see Patent Document 4). According to the invention disclosed in Patent Document 4, the average luminance of the screen is calculated for each frame, and the amount of light of the backlight is increased or decreased according to the magnitude of this value, and the difference in apparent luminance is enlarged to sharpen the image. It emphasizes the feeling and lowers the amount of light of the backlight for a screen with low luminance, so that the power consumption of the backlight can be reduced as a secondary effect.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-148807 (pages 2 to 4, FIG. 6)
[0006]
[Patent Document 2]
Japanese Patent Application Laid-Open No. 9-31317 (second to fourth pages, FIG. 1)
[0007]
[Patent Document 3]
JP-A-11-55598 (pages 2 to 5, FIG. 1)
[0008]
[Patent Document 4]
JP 2001-343957 A (1st to 4th pages, 9th page, FIG. 15)
[0009]
[Problems to be solved by the invention]
The conventional technique described above does not have the object of reducing the power consumption by controlling the amount of light of the backlight, except for the one disclosed in Patent Document 4, and the effect cannot be naturally obtained. Further, the conventional technology disclosed in Patent Document 4 aims at enhancing the effect of expressing a video, and the reduction in power consumption by controlling the light amount of the backlight is only a secondary effect. Moreover, depending on the average luminance of the displayed screen, the effect of reducing the average luminance may not be obtained much.
[0010]
Therefore, the present invention provides an image display method capable of appropriately controlling the amount of light of a backlight and reducing the power consumption of an image display device, irrespective of the average luminance of a screen, etc. The purpose is to provide equipment.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an image display method according to the present invention is directed to an image display method for displaying an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format. Is converted into an image signal of a luminance signal component and a color difference signal component, the luminance signal component is emphasized and inversely transformed into an RGB format image signal, and an image is displayed on the display screen by the inversely transformed image signal. The light amount of the backlight is reduced.
[0012]
According to the present invention, it is possible to achieve a reduction in power consumption of an image display device by reducing the amount of light of a backlight without impairing the apparent brightness of a screen by emphasizing a luminance signal component in an input image signal. Can be.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a system diagram of the image display device according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a control unit, which is constituted by, for example, a microprocessor. Reference numeral 2 denotes a conversion unit, reference numeral 3 denotes a luminance enhancement unit, and reference numeral 4 denotes an inverse conversion unit, which are constituted by a memory or an arithmetic processor. 5 is a multiplexer. Reference numeral 6 denotes a frame memory for reading and writing information of an image to be displayed in a frame unit, which is usually provided with two systems, and is configured to be able to write to one and read from the other.
[0014]
Reference numeral 7 denotes an LCD (liquid crystal) module, which is the most common display device of a backlight irradiation type. Reference numeral 8 denotes a display control unit, which may be included in the control unit 1 in terms of hardware configuration. Reference numeral 9 denotes a backlight module, and reference numeral 10 denotes a backlight power supply.
[0015]
FIG. 2 is a system diagram of a portable wireless communication device which is an example of an electronic device in which the image display device whose system diagram is shown in FIG. In the figure, reference numerals 1 to 10 are common to FIG. 11 is an antenna. Reference numeral 12 denotes a wireless unit, which includes a transmitting unit and a receiving unit. 13 is a modulation / demodulation unit, 14 is a vocoder unit for performing voice coding and decoding of coded voice, 15 is an AD / DA / voice / electric conversion unit which performs conversion between analog and digital and between voice and electric signals, and 16 is a receiver , 17 are transmitters. Reference numeral 18 denotes an operation input unit, and 19 denotes a power supply unit including a battery. Reference numerals 11 to 19 are generally included in the configuration of the portable wireless communication device.
[0016]
Further, with reference to FIG. 3 and FIG. 4, the operation of each unit and the flow of processing in the first embodiment of the present invention will be described. FIG. 3 is a flowchart of the first embodiment of the present invention. Prior to the start of the processing shown in FIG. 3, the control unit 1 is in a state where it can output an image signal in RGB format representing an image to be displayed on the LCD module 7 and operates the operation input unit 18 It is assumed that the content of the setting operation for the light amount of the backlight module 9 (selection of the normal value mode or the power saving mode with a value smaller than the normal value) performed through the backlight module 9 is held.
[0017]
When the process is started, the control unit 1 confirms the content of the setting operation for the light amount of the backlight module 9 and, if the “power saving mode” is selected (“YES” in step S1), the light amount is reduced. The backlight power supply 10 is controlled so as to match the power mode value (step S2). Further, it outputs an RGB format image signal to be displayed on the LCD module 7 to the converter 2. The conversion unit 2 converts the RGB image signal input from the control unit 1 into a format represented by a luminance signal component Y and color difference signal components Cb and Cr by the following conversion formula based on the specification of ITU-R BT601, for example. (Step S3). The conversion formula is shown below.
[0018]
Y = 0.257R + 0.504G + 0.098B + 16
Cr = -0.148R-0.291G + 0.439B + 128
Cb = 0.439R-0.368G-0.071B + 128
The conversion unit 2 is configured by, for example, a memory, and reads out the values of Y, Cb, and Cr previously written at an address uniquely corresponding to the combination of the values of R, G, and B of the input RGB format image signal. And can be realized. Since this method is processing by hardware, it can be performed at high speed. If there is no problem in terms of processing speed, it can be realized by software processing using the control unit 9 or a dedicated arithmetic processing processor.
[0019]
Subsequent to the process in the conversion unit 2, the brightness enhancement unit 3 performs a correction process for enhancing the brightness signal component Y (step S4). This processing can be realized by a method similar to gamma correction used to correct the relationship between the input voltage to the display and the brightness of the display, for example. FIG. 4 is a diagram illustrating the input / output characteristics of the luminance emphasizing unit 3 according to the first embodiment of the present invention using curves in the drawing. The horizontal axis of the drawing represents the input level to the luminance emphasizing unit 3 and the vertical axis represents the output level of the luminance emphasizing unit 3. The straight line represented by the broken line represents, for reference, a linear input / output characteristic when no luminance correction is performed.
[0020]
Here, when the luminance signal of the “Y1” value is input to the luminance emphasizing unit 3, the luminance emphasizing unit 3 outputs not the “Y1” value when the luminance correction is not performed, but the “Y1c” value larger than that. Is output. That is, since the brightness enhancement in the brightness enhancement unit 3 can improve the brightness corresponding to “Y1c−Y1”, the apparent brightness of the screen can be reduced even if the light amount of the backlight 9 is reduced by the corresponding amount. It will not change.
[0021]
The luminance emphasizing unit 3 can be realized by, for example, a memory, and reading out the value (Y1c) of the output luminance signal previously written at an address corresponding to the value (Y1) of the input luminance signal. Since this method is processing by hardware, it can be performed at high speed. If there is no problem in terms of processing speed, it can be realized by software processing using the control unit 9 or a dedicated arithmetic processing processor.
[0022]
The image signal in which the luminance signal component Y output from the luminance emphasizing unit 3 is emphasized is then converted by the inverse conversion unit 4 into an image signal expressed in the RGB format again for display on the LCD module 7 ( Step S5). The conversion equation in this case is expressed as follows by solving the conversion equation used in the conversion unit 2 for R, G, and B.
[0023]
R = 1.164 (Y-16) +1.596 (Cr-128)
G = 1.164 (Y-16) -0.391 (Cb-128) -0.813 (Cr-128)
B = 1.164 (Y-16) +2.018 (Cb-128)
The inverse conversion unit 4 is configured by, for example, a memory, and reads R, G, and B values previously written at addresses uniquely corresponding to combinations of Y, Cb, and Cr values of an input image signal. Can be realized. Since this method is processing by hardware, it can be performed at high speed. If there is no problem in terms of processing speed, it can be realized by software processing using the control unit 9 or a dedicated arithmetic processing processor. The RGB format image signal output from the inverse converter 4 is input to the multiplexer 5.
[0024]
Next, returning to step S1, a case where the content of the setting operation for the light amount of the backlight module 9 is the selection of the "normal value mode" will be described. In this case, the control unit 1 controls the backlight power supply 10 so that the light amount of the backlight module 9 matches the normal value (step S6). Further, the control unit 1 directly outputs an RGB format image signal to be displayed on the LCD module 7 to the multiplexer 5.
[0025]
In response to the selection signal from the control unit 1, the multiplexer 5 outputs the RGB output from the control unit 1 when the content of the setting operation for the light amount of the backlight module 9 is set to “normal value mode”. The image signal of the format is selectively output, and when the "power saving mode" is set, the image signal of the RGB format in which the luminance signal component output from the inverse converter 4 is emphasized is selectively output (step S7).
[0026]
The RGB format image signal output from the multiplexer 5 is written into the frame memory 6 under the control of the display control unit 8 and read out in synchronization with the driving of the LCD module 7 by a normal method for image display. Then, an image is displayed on the screen of the LCD module 7 (step S8). At this time, the amount of light of the backlight module 9 is controlled to be raised or lowered in accordance with the presence or absence of luminance enhancement of the displayed image signal as described above, and the apparent screen brightness does not change in either case. That is, the control unit 1 controls the light amount of the backlight module 9 by increasing or decreasing the voltage of the backlight power supply 10 according to the presence or absence of the luminance enhancement of the image signal.
[0027]
According to the first embodiment of the present invention, by enhancing the luminance signal component in the image signal, the amount of light of the backlight is reduced without impairing the apparent screen brightness, and the power consumption of the image display device is reduced. Can be reduced. Since image signal components other than the luminance component are not manipulated, there is basically no difference between the case where luminance enhancement is performed and the case where luminance enhancement is not performed in terms of overall image quality. It depends on other technical factors (for example, non-uniformity of each pixel of the LCD module 7) and the subjectivity of the viewer. If conceivable, the selection can be made depending on whether the image quality or the power consumption is prioritized.
[0028]
It is obvious that the above description also applies to an electronic device other than the image display device using the backlight irradiation type display device other than the LCD module and the portable wireless communication device. Further, the conversion equation of the image signal is not limited to the one described here.
[0029]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment of the present invention, when it is necessary to select the image quality or the power consumption as described above, the selection is made based on the presence or absence of the luminance enhancement. In the second embodiment of the present invention, a plurality of luminance enhancements can be selected as described below.
[0030]
FIG. 5 is a system diagram of the image display device according to the second embodiment of the present invention. In the figure, components that are the same as those in the first embodiment are denoted by the same reference numerals as in FIG. A demultiplexer 51 outputs an input signal to a selected distribution destination. Reference numerals 31 to 33 denote luminance emphasizing units A to C, respectively, which can be realized in the same manner as the luminance emphasizing unit 3 in the first embodiment. As will be described later, the luminance emphasizing units A31 to C33 differ in the degree of emphasis of the luminance signal components. In FIG. 5, the number of distributions is tentatively set to four, but is not limited to this.
[0031]
Reference numeral 52 denotes a multiplexer, which in the second embodiment, selects and outputs 1 from each output signal of the luminance emphasizing units A31 to C33 and the output signal directly output from the demultiplexer 51. .
[0032]
FIG. 6 is a system diagram of a portable wireless communication device which is an example of an electronic device having the image display device shown in the system diagram of FIG. In the figure, reference numerals 11 to 19 are common to FIG. 2, and the other components are common to FIG.
[0033]
Here, the input / output characteristics of the luminance enhancement sections A31 to C33 are represented by the curves in FIG. A straight line C0 in the figure represents a linear input / output characteristic when no luminance enhancement is performed, and curves C1 to C3 represent input / output characteristics of the luminance enhancement sections A31 to C33, respectively. The degree of luminance enhancement is largest at C3, and then decreases in the order of C2 and C1, and no luminance enhancement is performed at C0.
[0034]
Next, an operation of the image display device according to the second embodiment of the present invention will be described with reference to FIGS. The control unit 1 selectively controls the channels of the demultiplexer 51 and the multiplexer 52 based on the setting operation on the light amount of the backlight module 9 performed through the operation input unit 18. For example, when the image signal from the conversion unit 2 is selectively input to the luminance enhancement unit B32 by the demultiplexer 51, the image signal whose luminance has been enhanced by the luminance enhancement unit B32 is selected from the multiplexer 52 and output to the inverse conversion unit 4. Selection control is performed as follows.
[0035]
In this way, any one of the image signals whose luminance has been enhanced in four steps, including the case where the luminance is not enhanced, is selected and input to the inverse converter 4. At the same time, the control unit 1 controls the backlight power supply 10 so as to set the light amount of the backlight module 9 by switching stepwise.
[0036]
That is, when the input / output characteristic C0 of the luminance enhancement is selected, the light amount is set to a normal light amount, and the light amount of the backlight module 9 is reduced in the order in which C1, C2, and C3 are selected. Even in this case, the apparent brightness of the screen does not change because the luminance signal component in the image signal is emphasized so as to correspond to the decrease in the amount of light.
[0037]
The operation of the inverse transform unit 4 is the same as that in the first embodiment, and the description is omitted. In the first embodiment, an image signal which is not to be a luminance-enhanced image signal is selected by the multiplexer 5 at the subsequent stage of the inverse conversion unit 4. However, in the second embodiment, an image which is not luminance-enhanced is selected. Since the signal is already included in the selection and has already been selected in the multiplexer 52, the output of the inverse conversion unit 4 is directly input to the frame memory 6. Subsequent operations until the image is displayed on the screen of the LCD module 7 are the same as those in the first embodiment, and thus the description thereof will be omitted.
[0038]
According to the second embodiment of the present invention, since the range of choices can be increased in consideration of the power consumption and the visibility of the screen as compared with the first embodiment, the convenience can be further improved. it can.
[0039]
It is obvious that the above description also applies to an electronic device other than the image display device using the backlight irradiation type display device other than the LCD module and the portable wireless communication device.
[0040]
(Third embodiment)
Finally, a third embodiment of the present invention will be described with reference to FIG. The third embodiment of the present invention is designed to reduce the circuit configuration of the second embodiment, as described below.
[0041]
FIG. 8 is a system diagram of the image display device according to the third embodiment of the present invention. In the figure, reference numeral 35 denotes a luminance emphasizing unit realized by an arithmetic processor, which realizes the same functions as those realized by the multiplexer 51, the luminance emphasizing units A31 to C33, and the multiplexer 52 in FIG. 5 by software processing. . Other configurations are the same as those in FIG.
[0042]
According to the third embodiment of the present invention, the same effect as that of the second embodiment can be realized with a smaller circuit scale, and the degree of luminance enhancement (input / output characteristics) can be changed. Is also possible, and a secondary effect of high flexibility in use can be obtained.
[0043]
【The invention's effect】
According to the present invention, even if the light amount of the backlight of the image display device is reduced, the apparent brightness of the screen does not decrease, so that the power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram of an image display device according to a first embodiment of the present invention.
FIG. 2 is a system diagram of the portable wireless communication device according to the first embodiment of the present invention.
FIG. 3 is a flowchart according to the first embodiment of the present invention.
FIG. 4 is an input / output characteristic of a brightness enhancement unit according to the first embodiment of the present invention. FIG. 5 is a system diagram of an image display device according to a second embodiment of the present invention.
FIG. 6 is a system diagram of a portable wireless communication device according to a second embodiment of the present invention.
FIG. 7 is an input / output characteristic of a brightness enhancement unit according to a second embodiment of the present invention. FIG. 8 is a system diagram of an image display device according to a third embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 control unit 2 conversion unit 3 brightness enhancement unit 4 inverse conversion unit 5 multiplexer 6 frame memory 7 LCD module 8 display control unit 9 backlight module 10 backlight power supply 11 antenna 12 radio unit 13 modulation / demodulation unit 14 vocoder unit 15 AD / DA -Voice / electricity conversion unit 16 Receiver 17 Transmitter 18 Operation input unit 19 Power supply unit 31 Brightness enhancement unit A
32 Brightness enhancement section B
33 Luminance emphasis section C
35 brightness enhancement section 51 demultiplexer 52 multiplexer

Claims (11)

An image display method for displaying an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format,
Converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
The luminance signal component is emphasized and inversely converted into an RGB format image signal;
An image display method, comprising: displaying an image on the display screen using the image signal after the inverse conversion to reduce the amount of light of the backlight. An image display method for displaying an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format,
Converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
The luminance signal component is emphasized and inversely converted into an RGB format image signal;
Selecting one of the input image signal or the image signal after the inverse conversion, and when the input image signal is selected, the light amount of the backlight is relatively increased, and the image signal after the inverse conversion is selected. An image display method for displaying an image by relatively lowering the amount of light of the backlight when the image is displayed. 3. The image display according to claim 2, wherein the degree of enhancement of the luminance signal component can be selected or changed, and the amount of light of the backlight can be selected or changed correspondingly. Method. An image display device that displays an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format,
Conversion means for converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
Enhancing means for enhancing the luminance signal component;
Inverse conversion means for inversely converting the image signal of the emphasized luminance signal component and the color difference signal component into an image signal of an RGB format,
An image display device, wherein an image is displayed on the display screen based on the image signal output from the inverse conversion means, and the light amount of the backlight is reduced. An image display device that displays an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format,
Conversion means for converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
Enhancing means for enhancing the luminance signal component;
Inverse conversion means for inversely converting the image signal of the emphasized luminance signal component and the color difference signal component into an image signal of RGB format;
Selecting means for selecting any one of the input image signal or the image signal after the inverse conversion,
Light control means capable of relatively increasing the light amount of the backlight when the input image signal is selected, and relatively reducing the light amount of the backlight when the image signal after the inverse conversion is selected. An image display device comprising: The enhancing means may select or change the degree of enhancement of the luminance signal component obtained from the converting means and provide the input to the inverse converting means, and the dimming means may select or change the degree of enhancement. The image display device according to claim 5, wherein the amount of light of the backlight can be selected or changed in response to the change. The said conversion means, the emphasis means, or the said reverse conversion means was comprised by the memory in which the level of the output image signal was written in the address corresponding to the level of the input image signal. The image display device according to any one of claims 4 to 6. In an electronic apparatus having a main body and an image display device provided on the main body and displaying an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format, the image display device includes:
Conversion means for converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
Enhancing means for enhancing the luminance signal component;
Inverse conversion means for inversely converting the image signal of the emphasized luminance signal component and the color difference signal component into an image signal of an RGB format,
An electronic apparatus, wherein an image is displayed on the display screen based on the image signal output from the inverse conversion unit, and the light amount of the backlight is reduced. In an electronic apparatus having a main body and an image display device provided on the main body and displaying an image on a display screen illuminated by a backlight based on an input image signal expressed in an RGB format, the image display device includes:
Conversion means for converting the input image signal into an image signal of a luminance signal component and a color difference signal component,
Enhancing means for enhancing the luminance signal component;
Inverse conversion means for inversely converting the image signal of the emphasized luminance signal component and the color difference signal component into an image signal of RGB format;
Selecting means for selecting any one of the input image signal or the image signal after the inverse conversion,
Light control means capable of relatively increasing the light amount of the backlight when the input image signal is selected, and relatively reducing the light amount of the backlight when the image signal after the inverse conversion is selected. An electronic device comprising: The enhancing means may select or change the degree of enhancement of the luminance signal component obtained from the converting means and provide the input to the inverse converting means, and the dimming means may select or change the degree of enhancement. 10. The electronic device according to claim 9, wherein the amount of light of the backlight can be selected or changed in response to the change. The said conversion means, the emphasis means, or the said reverse conversion means was comprised by the memory in which the level of the output image signal was written in the address corresponding to the level of the input image signal. The electronic device according to any one of claims 8 to 10.

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